From: Paolo Abeni pabeni@redhat.com
[ Upstream commit b406472b5ad79ede8d10077f0c8f05505ace8b6d ]
Since commit c09551c6ff7f ("net: ipv4: use a dedicated counter for icmp_v4 redirect packets") we use 'n_redirects' to account for redirect packets, but we still use 'rate_tokens' to compute the redirect packets exponential backoff.
If the device sent to the relevant peer any ICMP error packet after sending a redirect, it will also update 'rate_token' according to the leaking bucket schema; typically 'rate_token' will raise above BITS_PER_LONG and the redirect packets backoff algorithm will produce undefined behavior.
Fix the issue using 'n_redirects' to compute the exponential backoff in ip_rt_send_redirect().
Note that we still clear rate_tokens after a redirect silence period, to avoid changing an established behaviour.
The root cause predates git history; before the mentioned commit in the critical scenario, the kernel stopped sending redirects, after the mentioned commit the behavior more randomic.
Reported-by: Xiumei Mu xmu@redhat.com Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Fixes: c09551c6ff7f ("net: ipv4: use a dedicated counter for icmp_v4 redirect packets") Signed-off-by: Paolo Abeni pabeni@redhat.com Acked-by: Lorenzo Bianconi lorenzo.bianconi@redhat.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/ipv4/route.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)
--- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -916,16 +916,15 @@ void ip_rt_send_redirect(struct sk_buff if (peer->rate_tokens == 0 || time_after(jiffies, (peer->rate_last + - (ip_rt_redirect_load << peer->rate_tokens)))) { + (ip_rt_redirect_load << peer->n_redirects)))) { __be32 gw = rt_nexthop(rt, ip_hdr(skb)->daddr);
icmp_send(skb, ICMP_REDIRECT, ICMP_REDIR_HOST, gw); peer->rate_last = jiffies; - ++peer->rate_tokens; ++peer->n_redirects; #ifdef CONFIG_IP_ROUTE_VERBOSE if (log_martians && - peer->rate_tokens == ip_rt_redirect_number) + peer->n_redirects == ip_rt_redirect_number) net_warn_ratelimited("host %pI4/if%d ignores redirects for %pI4 to %pI4\n", &ip_hdr(skb)->saddr, inet_iif(skb), &ip_hdr(skb)->daddr, &gw);